The invention disclosed herein relates generally to inspection of using robots and in particular to inspection of welds of jet pump diffusers and jet pump adapters in boiling water nuclear reactors (BWRs).
BWRs typically include jet pumps that participate in recirculating water through the reactors. An array of jet pumps are generally located around the circumferential periphery of the reactor vessel in the BWR. In a typical BWR, there are commonly ten jet pumps each with a pair of diffusers that direct water to the jet pump. Each of the twenty diffusers is attached to or extend past a horizontal baffle plate between the reactor vessel wall and a outer wall of the reactor. While many BWRs have jet pump diffusers that are welded directly to the baffle plates, some reactors attach the jet pump diffusers to an adapter located below the baffle plate. The inspection crawler and method disclosed herein may be used to inspect welds of jet pump diffusers that extend down past the baffle plate.
Inspection of the welds between the adapter and diffusers is needed to monitor the integrity of the diffusers and water recirculation system. Inspecting welds of the adapter and diffuser requires an inspection scanner to traverse a narrow gap between the baffle plate and diffuser. The narrow gap has been problematic in inserting ultrasonic inspection scanners down passed the baffle plate to inspect the welds attaching the adapter and diffuser. There is a long felt need for devices to inspect welds of diffusers below a baffle plate.